Fast 3D in vivo swept-source optical coherence tomography using a two-axis MEMS scanning micromirror

We report on a fibre-based forward-imaging swept-source optical coherence tomography system using a high-reflectivity two-axis microelectromechanical scanning mirror for high-speed 3D in vivo visualization of cellular-scale architecture of biological specimens. The scanning micromirrors, based on electrostatic staggered vertical comb drive actuators, can provide +/- 9 degrees of optical deflection on both rotation axes and uniform reflectivity of greater than 90% over the range of imaging wavelengths (1260-1360 nm), allowing for imaging turbid samples with good signal-to-noise ratio. The wavelength-swept laser, scanning over 100 nm spectrum at 20 kHz rate, enables fast image acquisition at 10.2 million voxels s(-1) (for 3D imaging) or 40 frames s-1 (for 2D imaging with 500 transverse pixels per image) with 8.6 mu m axial resolution. Lateral resolution of 12.5 mu m over 3 mm field of view in each lateral direction is obtained using ZEMAX optical simulations for the lateral beam scanning system across the scanning angle range of the 500 mu m x 700 mu m micromirror. We successfully acquired en face and tomographic images of rigid structures (scanning micromirror), in vitro biological samples (onion peels and pickle slices) and in vivo images of human epidermis over 2 x 1 x 4 mm(3) imaging volume in real time at faster-than-video 2D frame rates. The results indicate that our system framework may be suitable for image-guided minimally invasive examination of various diseased tissues.